Automotive ignition systems generally employ a power switching circuit that alternately makes and breaks an electrical connection from the vehicle battery, through an ignition coil to ground. The switching is typically based on a signal received from an engine control unit, which is timed to fire the engine spark plugs as needed for operation of the engine (e.g., for initiating fuel combustion cycles in the engine). The switching circuit, which may be implemented as an integrated circuit (IC), uses a supply voltage to power the circuit and its constituent components. This supply voltage is generally provided from a battery voltage of the vehicle battery and may, therefore, include high voltage transients, large voltage swings, high frequency noise and other artifacts (e.g., electrostatic discharge (ESD)) that can be detrimental to the operation and/or reliability of the switching circuit.
Additional protection circuitry can be used to protect the switching circuit IC from these voltage transients, large voltage swings, and high frequency noise as well as from electrostatic discharge (ESD). The protection circuitry, which may include large resistors and capacitors, can consume up to half of the switching circuit IC area, or more, in some cases. This typically results in increased size and cost of the switching circuit IC and may adversely impact reliability if the harsh environmental conditions imposed by the vehicle battery are not adequately filtered by the protection circuitry.